In Euclidean geometry, triangles are considered as one of its basic figures. A shape must contain three elements in order for it to be considered a triangle. First, it needs to have three sides. It also haveto be a plane or two dimensional figure, and finally, the sum of the interior angles must be equal to 180 degrees.

There are two recognized ways or systems for classifying triangles. One system focuses on the sides and based on this it designates three types of triangles:

• Equilateral triangles are triangles with equal sides. In this type of triangle all three sides of the figure have the same length. Since the angles are also going to be equal (all at 160 degrees), this triangle is also equiangular.

• Isosceles triangles has two sides that have the same length. What this also means is that the two angles that are formed at the point where the equal sides met the third side are equal.

• Scalene triangles have all three sides that are unequal. This also means that the angles in the shape are also unequal.

The other system of classifying triangles is based on the viwing the measurement of the internal angles. Based on this classification, there are three triangles:

• Acute triangles has its internal angle measured at less than 90 degrees.

• Right triangles has one right angle – which is an angle that is exactly measured at 90 degrees. With this type of triangle, the two remaining angles are acute.

• Obtuse triangles have one internal angle that is obtuse. The two remaining angles are also acute.